ÔØ ÅÒÙ×Ö ÔØ Carbon cycle history through the Jurassic–Cretaceous boundary: A new global δ13C stack Gregory D. Price, Istv´an F˝ozy, J´ozsef P´alfy PII: S0031-0182(16)30024-4 DOI: doi: 10.1016/j.palaeo.2016.03.016 Reference: PALAEO 7749 To appear in: Palaeogeography, Palaeoclimatology, Palaeoecology Received date: 25 November 2015 Revised date: 11 March 2016 Accepted date: 17 March 2016 Please cite this article as: Price, Gregory D., F˝ozy, Istv´an, P´alfy, J´ozsef, Carbon cycle history through the Jurassic–Cretaceous boundary: A new global δ13Cstack,Palaeo- geography, Palaeoclimatology, Palaeoecology (2016), doi: 10.1016/j.palaeo.2016.03.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT Carbon cycle history through the Jurassic-Cretaceous boundary: a new global 13C stack Gregory D. Price1, István Főzy2, József Pálfy3, 4 1School of Geography, Earth & Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom ([email protected]) 2Department of Paleontology and Geology, Hungarian Natural History Museum, POB 137, Budapest, H- 1431 Hungary ([email protected]) 3Department of Physical and Applied Geology, Eötvös Loránd University, Pázmány P. sétány 1/C, Budapest, H-1117 Hungary ([email protected]) 4MTA-MTM-ELTE Research Group for Paleontology, POB 137, Budapest, H-1431 Hungary ABSTRACT We present new carbonACCEPTED and oxygen isotope curves MANUSCRIPT from sections in the Bakony Mts. (Hungary), constrained by biostratigraphy and magnetostratigraphy in order to evaluate whether carbon isotopes can provide a tool to help establish and correlate the last system boundary remaining undefined in the Phanerozoic as well provide data to better understand the carbon cycle history and environmental drivers during the Jurassic-Cretaceous interval. We observe a gentle decrease in carbon isotope values through the Late Jurassic. A pronounced shift to more positive carbon isotope values does not occur until the Valanginian, corresponding to the Weissert event. In order to place the newly obtained stable 1 ACCEPTED MANUSCRIPT isotope data into a global context, we compiled 31 published and stratigraphically constrained carbon isotope records from the Pacific, Tethyan, Atlantic, and Boreal realms, to produce a new global δ13C stack for the Late Oxfordian through Early Hauterivian interval. Our new data from Hungary is consistent with the global δ13C stack. The stack reveals a steady but slow decrease in carbon isotope values until the Early Valanginian. In comparison, the Late Jurassic–Early Cretaceous δ13C curve in GTS 2012 shows no slope and little variation. Aside from the well-defined Valanginian positive excursion, chemostratigraphic correlation durSchning the Jurassic–Cretaceous boundary interval is difficult, due to relatively stable δ13C values, compounded by a slope which is too slight. There is no clear isotopic marker event for the system boundary. The long-term gradual change towards more negative carbon isotope values through the Jurassic-Cretaceous transition has previously been explained by increasingly oligotrophic condition and lessened primary production. However, this contradicts the reported increase in 87Sr/86Sr ratios suggesting intensification of weathering (and a decreasing contribution of non-radiogenic hydrothermal Sr) and presumably a concomitant rise in nutrient input into the oceans. The concomitant rise of modern phytoplankton groups (dinoflagellates and coccolithophores) would have also led to increased primary productivity, making the negative carbon isotope trend even more notable. We suggest thatACCEPTED gradual oceanographic changes,MANUSCRIPT more effective connections and mixing between the Tethys, Atlantic and Pacific Oceans, would have promoted a shift towards enhanced burial of isotopically heavy carbonate carbon and effective recycling of isotopically light organic matter. These processes account for the observed long-term trend, interrupted only by the Weissert event in the Valanginian. Keywords: Late Jurassic; Early Cretaceous; chemostratigraphy; carbonate carbon cycle history 2 ACCEPTED MANUSCRIPT 1. Introduction The Jurassic-Cretaceous transition is a relatively poorly understood interval in the development of the Mesozoic greenhouse world (Föllmi, 2012; Price et al., 2013). This is, in part, due to the lack of an agreed upon, chronostratigraphic framework for the Jurassic-Cretaceous boundary (Zakharov et al., 1996; Wimbledon et al., 2011; Michalík and Reháková, 2011; Guzhikov et al., 2012; Shurygin and Dzyuba, 2015). It is a time of contentious biotic changes, for which opinions have ranged from proposal of a putative mass extinction (Raup and Sepkoski, 1984) or a regional event (Hallam, 1986) or non- event (Alroy, 2008; Rogov et al., 2010). Using large taxonomic occurrence databases, several recent studies (particularly of tetrapods) have re-examined the Jurassic-Cretaceous boundary, and note a sharp decline in diversity around the Jurassic-Cretaceous boundary (Barrett et al., 2009; Mannion et al., 2011; Upchurch et al., 2011; Tennant et al., 2016). Further, the boundary interval is characterized by elevated extinction and origination rates in calcareous nannoplankton (Bown, 2005) set against a background of several calpionellid diversification events (Remane, 1986; Michalík et al., 2009) and an evolutionary rise of the modern plankton groups, notably dinoflagellates and coccolithophores (Falkowski et al., 2004). The system boundary also presents persistent stratigraphic correlation ACCEPTED MANUSCRIPT problems, which explains why the Jurassic–Cretaceous boundary is the only Phanerozoic system boundary for which a GSSP (Global Stratotype Section and Point) remains to be defined (Wimbledon, 2008; Wimbledon et al., 2011). The problems in global correlation of the Jurassic–Cretaceous boundary arise from the lack of an agreed upon biostratigraphical marker, in part related to general regression leading to marked provincialism in different fossil groups. The Tethyan based ammonite definition for the base of the Cretaceous has been the base of the Jacobi Zone (e.g., Hoedemaeker et al., 1993), although the base of which falls within the middle of relatively long sub-Boreal Preplicomphalus Zone 3 ACCEPTED MANUSCRIPT and the Boreal Nodiger Zone. Other definitions of the Jurassic–Cretaceous boundary (see Grabowski, 2011; Wimbledon et al., 2011) include the base of Grandis ammonite Subzone, in the lower part of calpionellid Zone B, almost coinciding with the base of magnetozone M18r (Colloque sur la Crétacé inferieur, 1963) or the boundary between Grandis and Subalpina ammonite subzones, correlated with the middle part of calpionellid Zone B and the lower part of magnetozone M17r (Hoedemaeker, 1991). Due to scarcity of ammonites in many Tethyan Tithonian and Berriasian successions, calpionellids have been used as the main biostratigraphic tool in some studies (e.g., Horváth and Knauer, 1986; lau and r n, 1997; Houša et al., 2004; oughdiri et al., 2006; Michalík et al., 2009; rabowski et al., 2010a). The base of Calpionella Zone (B Zone) and the sudden appearance of a monospecific association of small, globular Calpionella alpina (referred to by authors as the alpina "acme", Remane 1985; Remane et al., 1986) is sometimes used as an indicator of the Jurassic-Cretaceous boundary. The base of reversed- polarity chron M18r has also been suggested as a convenient global correlation horizon near the clustering of these possible biostratigraphic-based boundaries (Ogg and Lowrie, 1986). The recognition of this magnetozone across provincial realms (e.g., Ogg et al., 1991; Houša et al., 2007; Grabowski et al., 2010a) has enabled inter-regional correlations. In the GTS2012, Ogg and Hinnov (2012a) utilize the base ofACCEPTED chron M18r for assigning MANUSCRIPT the numerical age (145.0 Ma) to the top of the Jurassic. Notably, the base of chron M18r which falls within the middle of the Berriasella jacobi Zone. Hence, Wimbledon et al. (2011) , tentatively suggest that several markers have the potential to help define any putative Jurassic-Cretaceous boundary. Carbon isotope stratigraphy is useful both to help understand past global environmental and biotic change that affected carbon cycle, and as a correlation tool. For example, the GSSP for the base of the Eocene Series is defined by a negative excursion in the carbon isotope curve (Aubry et al., 2007). 4 ACCEPTED MANUSCRIPT To serve both purposes, Late Jurassic–Early Cretaceous carbon isotope stratigraphies have been developed extensively from pelagic sediments of the Tethys Ocean and Atlantic (e.g., Weissert and Channell, 1989; Bartolini et al., 1999; Katz et al., 2005; Tremolada et al., 2006; Michalík et al., 2009; Coimbra et al., 2009; Coimbra and Olóriz, 2012). Weissert and Channell (1989) documented how the Late Jurassic carbonate carbon isotopic composition shifts from δ13C values of around 2.5‰ in the Kimmeridgian to values near 1.0‰ in the Late Tithonian–Early Berriasian. A change to lower δ13C values was identified to occur within Magnetozones M18–M17 and within the B/C Calpionellid Zone (Weissert and